Left during the game, perhaps, the light being so weak (5)
I believe the answer is:
gleam
'light being so weak' is the definition.
I can't tell whether this defines the answer.
'left during the game perhaps' is the wordplay.
'left' becomes 'L' (common abbreviation).
'during' is an insertion indicator.
'perhaps' indicates anagramming the letters.
'game' with letters rearranged gives 'geam'.
'l' put within 'geam' is 'GLEAM'.
'the' acts as a link.
Can you help me to learn more?
(Other definitions for gleam that I've seen before include "Brightness" , "Glow of light" , "Moderate glow" , "Sparkle, glimmer" , "Beam of soft light, comes and goes" .)